My child have demonstrated what he imagined with a mockup and has a video, and would like apple or anyone to implement and market his idea and give him one. I better would like to have a patent for what he envisioned since it is really cool. What might be the vest venue to protect his idea and at the same time trigger its implementation?

Motorola came out with their Activ "watch" line that is essentially an android with gps, heartbeat, cadence etc. sensors. But as far I know, it didn't really take off. I'm guessing that an Apple version would be an instant success.

Single-digit milliamps is already very high drain for lithium primaries (a CR2450 is of order 550mAh, and the internal resistance soars as the thing drains). But if the user can be persuaded to dock the thing when not worn into a wired or wireless charging fixture, and we use rechargeables, there's hope.
Brad

Wearable computers are the predictable next step, in this "pervasive computing" trend that's been going on for many decades now. As usual, Star Trek already showed this, starting with Next Generation.
Beyond this step is the implanted ones.
Honestly, I'm not a die-hard trekie. Just pointing out that TV script writers are also creative people, and there's no reason to doubt that engineering will sooner or later catch up with their dreaming.